from Madrid, as well as El Escorial (which is usually part of the Madrid itnerary, but is outside the city). Those are good can't-miss highlights for first-time visitors. Barcelona is great, as is the southern coast of France.

You can see the main highlights of both Segovia and Toledo in daytrips, but I would suggest spending a night in at least one of them — summer nights are great in those smaller Spanish cities. You could also extend the tour of the area to include Salamanca (one of my favorite towns in Europe) and a stop in Avila, which has awesome medieval city walls. They would be easy to combine with a trip to Segovia, if you have an extra day or two. I guess it depends on how much time you want to spend in that part of Spain, as opposed to the Mediterranean coast.

As for Madrid itself, I would dedicate a full day to El Escorial, including getting there and back, and at least a half-day at El Prado (if you love art you can easily spend a full day there). I would also hit at least one of Madrid's other major art museums: Reina Sofia or Thyssen-Bornemisza. That's probably another half-day, or if you love art and visit both, then a full day. The royal palace and surrounding area (including the park) is very cool, you'll need a half-day for that. And the Plaza Mayor and central Madrid is at least another half-day. If you like soccer or sports you could try to hit the Santiago Bernabeu stadium where Real Madrid plays, they do tours there. There is a great monastery called the Monasterio de las Descalzas Reales in central Madrid, and a house-museum in an old mansion I like called the Cerralbo Museum. There is also a great National Anthropology museum, if you like history and anthropolgy. Anyway, all told I would recommend at least 3 full days in Madrid, and maybe 4, including El Escorial, but excluding daytrips to other towns.

Barcelona itself is at least 2-3 days, and maybe more if you want to hang out on the beach for a half-day. The highlights for me there are the Sagrada Familia basilica, Las Ramblas walking street, the waterfront, the Gaudi houses (La Pedrera is great), Parc Guell, the medieval quarter (Barri Gotic), and the Picasso museum (if you like his stuff). There is an interesting medieval monastery outside the city called Monserrat, in a picturesque mountain location. And again, if you like soccer, you can tour the Camp Nou stadium where Barcelona plays.

I don't know Southern France as well, haven't spent as much time there. But I really like Nice, Antibes, and Marseilles, and of course Monaco is pretty cool. Avingon is a pretty medieval town inland from the coast that is worth visiting, maybe an hour north of Marseille by car/bus.